1. Field of the Invention
The present invention relates to a shield case of a high frequency device such as a tuner portion consisting, for example, an input circuit, a high frequency amplification circuit and a frequency conversion circuit of a television receiver.
2. Description of the Related Art
Generally speaking, the high frequency device of the tuner portion of a television receiver consisting of an input circuit, high frequency amplification circuit, etc. is covered with a metal case consisting, for example, of a tin plate, to effect electromagnetic wave shielding for electromagnetic wave disturbance.
As shown in FIGS. 1 and 2, the metal case of this conventional tuner portion comprises a rectangular box-like frame body 2 surrounding a circuit board 1 on which the high frequency parts of the input circuit, the high frequency amplification circuit and the frequency conversion circuit are mounted, and upper and lower case covers 2a and 2b, consisting, for example, tin plates, covering the upper and lower openings of this frame body 2.
As shown in FIG. 2, there is provided in this frame body 2 of the metal case a partition 3 consisting of a predetermined metal plate, for example, a tin plate, and a predetermined number of contact portions 3a are provided at predetermined positions of this partition 3. Further, formed at positions corresponding to the contact portions 3a of the partition 3 are thin and narrow claws 4 whose forward ends are free ends, the forward ends abutting the contact portions 3a of the partition 3, being electrically and mechanically connected thereto, providing predetermined high frequency characteristics (shield effect).
And, as a radiating part for dissipating heat, a heat sink S consisting of a metal plate such as an aluminum plate is mounted to the semiconductor integrated circuit IC mounted on the circuit board 1.
In this way, in the high frequency device of the tuner portion of the television receiver, when the heat sink 5 is mounted as the heat dissipating plate to the semiconductor integrated circuit IC mounted on the circuit board 1 in the metal case 2, the heat generated from the integrated circuit IC is dissipated effectively. However, the heat sink 5 is a member which is separate from the semiconductor integrated circuit IC, and it is mounted to the integrated circuit IC, which is to be cooled at the time of assembly, by using an adhesive, an adhesive tape, a screw or the like, so that it is troublesome.
Further, regarding the semiconductor integrated circuit IC accommodated in the metal case 2, there is a limitation to the configuration of the heat sink 5 in the limited space in the metal case 2, so that it is difficult to achieve high efficiency in heat dissipation. Thus, when a relatively large heat sink is used, the efficiency in heat dissipation is improved. However, it sticks out from the metal case 2, so that shield effect is reduced by half. Further, during the transportation of the product, the portion sticking out is not held properly, with the result that the packing box has to be rather large.
The present invention has been made in view of the above problems. Accordingly, it is an object of the present invention to provide a shield case in which it is possible to achieve, with a single part, the electromagnetic wave shielding for electromagnetic wave disturbance and the heat dissipation for the heat generating part.
To achieve the above object, there is provided in accordance with the present invention a metal shield case which encloses a circuit board on which an electronic circuit part is mounted, shielding electromagnetic wave disturbance, wherein a tongue is provided in a part of the shield case surface by a cutout, the tongue being held in press contact with the surface of a heat generating part mounted on the circuit board.
In this way, in accordance with the present invention, a tongue provided in a part of the shield case surface is held in press contact with the heat generating part of the electronic circuit accommodated in the shield case, whereby it is possible to obtain a high frequency characteristic (shield effect) and a cooling effect.